How is the size of irregular-shaped 3D particles converted into equivalent spheres?

There are different methods for converting the size of irregular-shaped 3D particles into equivalent spheres. The Heywood (spherical equivalent) diameter is the method used in most particle sizing technologies. The measurement method used will affect the results when reporting on an equivalent spherical diameter and average diameter will have a different bias and deviation from actual when using different technologies due to factors such as shape sensitivity and weighting affect for different particles in the sample.